The structure of the circular DNA molecule isolated from hepatitis B Dane particles and the mechanism of the Dane particle DNA polymerase will be analyzed using restriction endonucleases. Attempts will be made to infect tissue culture cells with Dane particles and Dane particle DNA. Infection will be tested for by immuno-fluorescence for HBsAG and HBcAg and radioimmunoassay for HBsAg. The state of hepatitis B virus and its mechanism of replication will be studied in a human hepatoma cell line in culture which produces HBsAg.